In a significant fraction of antiperspirant compositions, the active antiperspirant material is present in particulate form. For ease of dispensation, in many of such compositions, the active antiperspirant material is suspended or otherwise dispersed in a liquid carrier phase, often with the assistance of suspension agents or aids. If the antiperspirant material is not suitably suspended, there is a risk that it will tend to separate from the liquid carrier, for example by settling on the bottom of the container for the composition during storage or between applications. When the settled material can be readily redispersed by the user, such as by manual shaking of the applicator before use, solids settling constitutes a minor inconvenience rather than a significant problem. However, when the settling produces a compact layer which is extremely difficult or even impossible to redisperse manually, the problem attains serious proportions, because is extremely desirable to avoid or reduce the effective loss from the formulation of active antiperspirant material. Self-evidently, loss of active material during storage renders the composition non-uniform in application, with the risk that for a fraction of the time that the composition is used, it will be ineffective or insufficiently effective at controlling perspiration loss.
It has been found that advantageous skin sensory properties can be achieved by incorporating a polyglycol ether as at least part of the liquid phase in an antiperspirant composition. A practical way of suspending a particulate antiperspirant in a liquid carrier has comprised the incorporation of a suspending aid, often inorganic such as a clay. However, it has further been found that when the carrier comprises a polyglycol ether, the ability of the clay or like suspending agent to suspend or re-suspend the particulate antiperspirant material in the carrier liquid is significantly impaired.
It is known to surface treat particulate inorganic substances in other fields of activity, specifically pigments and sunscreens, but for other purposes. Thus, for example, titanium dioxide pigments are surface treated in GB-A-1602428 with esters or amines and this affects the rate at which films containing the pigment dry. In EP-A-0559319, metallic oxide particles, especially titanium dioxide and zinc oxide particles are surface coated to aid their suspension in aqueous emulsions. This is not relevant to predominantly anhydrous compositions of the present invention. Similarly in U.S. Pat. No. 5,573,753, dispersions of surface treated particulate titanium oxide and zinc oxide in an aqueous emulsion are described. In U.S. Pat. No. 4,318,843 (EP-A-0021262) there is described the surface treatment of inorganic pigments of which TiO.sub.2 is exemplified in order to improve its gloss and distribution in lacquer bindings. In U.S. Pat. No. 5,776,440, the effectiveness of metallic oxide to screen out UV-radiation when applied topically is enhanced by coated them with a wide range of organic compounds. The treatment of TiO2 is exemplified.
It is an object of the present invention to ameliorate or overcome one or more of the problems or disadvantages indicated hereinabove.